Efficacy and Efficiency

Efficacy refers to the ability of a product, service, or intervention to produce the desired result under ideal conditions—it answers "Does it work?" Efficiency, on the other hand, measures how well resources like time, money, and effort are used to achieve that result—it's about "How well does it work, given the resources?" In short, efficacy focuses on the success of the outcome, while efficiency emphasizes doing so with optimal use of resources. Both are important for evaluating performance, but they address different aspects of effectiveness and productivity.